Pancreas transplantation can benefit a person with type 1 diabetes with severe, frequent hypoglycemia. An alternative treatment is the transplantation of the insulin producing cells, isolated islets. These methods are limited due to the scarcity of pancreas and islets for donation. Rejection of the transplanted pancreas or islets from a donor is inevitable without co-administration of immunosuppressive agents. Immunosuppressive therapies also often results in undesirable side effects. Minimizing the amount of agents needed for suppression can significantly improve the living conditions of the subject. Thus, there is a need to identify improved therapeutic alternatives.
Adult porcine islet (API) xenografts are an alternate source of donor cells. Such a strategy is promising because transplantation of microencapsulated islet xenografts restores normoglycemia in nonobese diabetic (NOD) mice. Various immunoisolation strategies, including alginate microcapsules, have been reported to protect discordant islet xenografts from rejection for short periods. Chang et al., U.S. Pat. No. 5,084,350 describe the microencapsulation of biological materials using gels. Safley et al., J Diab Sci Tech, 2008, 2: 760, disclose adult porcine islets in calcium alginate poly-1-lysine (PLL) microcapsules. Unfortunately, certain alginate PLL microcapsules are not durable long-term. See also Cui et al., Transplantation, 2009, 88(2):160-169, U.S. Pat. Nos. 5,227,298, and 5,795,570. Thus, there is a need to identify improved vehicles.